Drafting board with magnetic t-square



June 16, 1964 w. B. TERRY 3,137,072

DRAFTING BOARD WITH MAGNETIC T-SQUARE Filed July 26, 1961 2 Sheets-Sheet 1 Fig./ 40 i i L 42 30 g I} 58 T -56 I 32 I ll 1| /4 l l: I PHCx-Nl p F5 11; 1 d 5 *0 v .1

William 5. Terry Fi 3 INVENTOR.

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June 16, 1964 W. B. TERRY DRAFTING BOARD WITH MAGNETIC T-SQUARE Filed July 26. 1961 2 Sheets-Sheet 2 Will/am 8. Terry 1N VEN TOR.

United States Patent O This invention comprises a novel and useful drafting board with magnetic T-square and more particularly relates to a drafting appliance having means for more effectively securing the T-square in proper position upon the drafting board and facilitating movement of the T-square with respect to the drafting board while maintaining the T-square in operative contact therewith.

In drafting it is extremely important to maintain the head of the T-square in firm but sliding contact with the edge of the drafting board in order that the blade of the T-square may be moved in parallel positions upon the drawing paper. It frequently occurs that the draftsmans hand may release momentarily his pressure upon the head of the T-square allowing the latter to deviate from its desired position upon the board perpendicular to the guide edge of the board. Moreover, owing to the sliding movement of the head of the T-square along the edge of the board there is considerable wear developed from time to time between the sliding surfaces which thus render somewhat inaccurate the useof the T-square.

It is therefore the primary object of this invention to provide a drafting'board and T-square construction which will effectively overcome the above mentioned difficulties.

A further object of the invention is to provide a drafting board and T-square construction which shall be simple and inexpensive, yet highly efiicient and of long life in its operation.

A still further object of the invention is to provide a drafting board having a reinforcing metallic member along its edge againstwhich the head of the T-square moves thereby providing at all times a truly straight surface for.

engagement by an alignment of the T-square and one which will be highly resistant to wear.

3,137,072 Patented June 16, 1964 ice :he combined roller and magnet means of the T-square ead;

FIGURE 4 is a view similar to FIGURE 1 but showing a slightly modified construction of T-square;

FIGURE 5 and FIGURE 6 are detail views in vertical transverse section taken substantially upon the plane indicated by section lines 55 and 66 respectively of FIGURE 4 and showing respectively the anti-friction roller means and the magnet means of this embodiment; FIGURE 7 is a perspective view of a unit containing therein the roller guide and magnet means of this embodiment of the invention; and

FIGURE 8 is an exploded perspective view of the unit of FIGURE 7. A

In both forms of the invention illustrated in the drawings the same construction of drafting board is provided as indicated bythe numeral 10. Upon that edge of the drafting board which is engaged by the customary head 12 of a T-square having a blade 14 there is provided a metallic edge plate 16. This edge plate includes a flat flange 18 which overlies the edge of the drafting board and provides a smooth surface upon which the T-square head is to be slidably engaged. The flange 18 in turn is provided with a bottom flange 20 having an upturned flange 22. The flanges 20 and 22 are embedded in the material of the board 10 so as to firmly secure in a rigid manner the metallic edge 16 to the board. This coni struction is identical for both forms of the invention,

Yet another object of the invention is to provide a drafting board and T-square in accordance with the foregoing objects wherein the T-square head shall include therein means for reducing the friction of the movement of the T-square along the guiding edge of the drafting board and further will automatically maintain the T-square in proper engagement with the edge of the drafting board.

Specifically, it is the primary purpose of this invention to provide a drafting board and T-square combination in which a magnetic reinforcing strip is provided along the edge of the drafting board which is engaged by a roller and magnet assembly of the T-square head for minimizing frictional contact and maintaining close con-- tact between these elements. H

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which: FIGURE 1 is a fragmentary top plan view showinga portion of-a drafting board and a T-square with the present invention applied thereto and the T-square and drafting board being shown in operative position for use bya draftsman certain concealed parts being shown in dotted lines therein;

FIGURE 2 is a fragmentary detail view in vertical longitudinal section taken substantially upon the plane 7 indicated by broken line 2--2 of FIGURE 1 and Shows the variation therein residing in the actual means provided upon the T-square head for slidably engaging the drafting board and retaining the head of the T-square against the edge 18 of the drafting borad.

The inner lengthwise straight-edge 32 of the T-square head 12 is notched at the respective end portions and also at its centralized or median portion to provide several equidistant recesses 30. Each recess (see FIG; 2) opens through the edge 32 and top and bottom surfaces of the head 12 and is substantially circular in plan, that is, of the shape and size illustrated in full and dotted lines in FIG. 1 and accordingly is adapted to house novel means which is provided to facilitate the sliding action of the head 12 against the edge of the'drafting board. In addition each recess is likewise adapted to houseand confine the cooperable permanent magnet in a manner to be hereinafter more fully described.

Referringnow primarily to FIGURES 1 3 it will be seen that there is provided for each of these recesses a permanent horseshoe type magnet 4-0 which is snugly received in the recess 30 and which has its pole pieces or legs 42 protruding slightly'beyond the edge 32 of the T-square head 12. Any suitable means may be provided for retaining and securing the magnet in the recess. Conveniently, for this purpose, the arrangement shown in FIGURE 2 may be provided in which the T-square head has a pair of top and bottom roller mounting plates each indicated by the numeral 44 and which are removably secured together about the T square headand cover and close the otherwise open top and bottom portions. of the several recesses 30, said plates being retainedin place, by means of fasteners 46 which likewise are employed to attach the blade 14 to the T-square head. Since the recesses 30 constitute more than one-half of a circle, it is obvious that the opening across the edge.32 is smaller in size than the diameter of the recess whereby the horseshoe magnets will be firmly retained therein while. possessing a slight degree of oscillatory movement for selfcentering or adjustment purposes.

There are also provided anti-friction rollers or spools indicated generally by the numeral 50 and which consists of a pair of roller disks 52 connected together by a hub 54 therebetween. that the roller disks may loosely embrace the sides of The size of these parts are such- I; the magnet pole pieces 42 in the manner shown in FIG- URE 2 while the spool piece 54 is received between the magnet pole pieces. Thus, there is provided a compact association of the anti-friction rollers with the magnets, the pole pieces or legs of the magnet serving as a means to receive, position, and journal or guide the rollers. As

will be further observed, the rollers are such size that they likewise protrude beyond the edge 32 of the T-square head and even below the pole pieces so that with the parts in the relation shown in FIGURES 1 and 2, the rollers will engage the edge 18 of the drafting board retaining thus the T-square edge 32 in slightly spaced relation from this edge as well as retaining the magnet pole pieces 42 in closely spaced relation from the T-square head. Thus, the magnets are rendered effective to hold the T-square head'against the edge of the drafting board thus insuring proper position of the T-square at all times. Obviously, any desired numbers of these units, each unit consisting of an anti-friction roller assembly 50 and a permanent magnet may be utilized. In order to further retain and insure proper association of the magnet and of the anti-friction roller, assemblies there is provided a pivot pin 56 together with a pair of spacer washers 58. The pin is adapted to be received through an axial bore 60 through the anti-friction roller assembly 50 and the ends of the pivot pin are engaged in corresponding bores 62 formed in the side walls 44, as shown in FIGURE 2.

In principle, the modified embodiment (FIGURES 4-'8) is quite similar to that disclosed in connection with FIG- URES 1-3. However, in this form of the invention the intimate association of the anti-friction rollers with the magnets of FIGURES 1-3 is replaced by a special arrangement. To the end desired a suitable housing 70 is provided, said housing consisting of a pair of side walls 72 and 74 together with a core-like insert or spacer block 76 therebetween of the same general shape. The spacer block or filler block is provided with a plurality of substantially circular recesses 78 and 80 therein, the recesses 78 serving to enclose anti-friction rollers 82 while the recess 80 receives a permanent magnet 84. One of the housing walls such as 72 is provided with an upstanding flange 86 which flange is adapted to overlie the edge 32 of the T-square head 12 to which it is appropriately secured as shown in FIGURES and 6; Suitable pins 88 are received in corresponding apertures 90 in the plate 72 and 74 and also extend through the apertures 2 of the rollers 82 and serve to rotatably journal these rollers in the unit 70. If desired, these pins may themselves be employed as rivets to retain the two plates 72 and 74 in fixed engagement upon the filler member 76. Likewise, Washers 94 are provided to suitably space the rollers 82 from the two plates of the units. As in the preceding form of the invention, both the rollers and the permanent magnets project from the housing unit 70 and also from the edge 32 of the T-square head a suflicient distance to enable the rollers to engage the straight edge 18 of the drafting board while the magnets aredisposed in proper position to apply a magnetic force tending to-retain the straight edge head against the drafting board edge.

It is to be noted that in both embodiments of the invention and as best illustrated in FIG. 1 and similarly illustrated in FIG. 4 at least three longitudinally spaced magnets are installed, one at each end (FIG. 1) and the rebe evident therefore that the T-square can be aptly used when the blade or leg 14 is in proximity to either the upper lengthwise edge of the board or the lower or bottom edge thereof as the case may be. This result could not be aptly or satisfactorily achieved if the magnet and roller assemblies were limited to the respective upper and lower positions illustrated, for example, in FIG. 1. It is also to be noted that in the construction illustrated, the magnets never physically touch the straight edge 18. Hence, there is no possibility of a T -square propelling itself even a minute distance.

It is also to be observed that the rollers 59 or 82, as

p the case may be, are preferably made of an appropriate grade of plastic material and are practically noiseless when in motion and rolling along the straight edge 18. It will be obvious that certain types of metal rollers, if used, and rolling against a steel bar or strip would no doubt produce an objectionable noise.

In'both embodiments of the invention (see FIGS. 1 and 2 and 4 and 5 in particular) the permanent magnets are substantially shielded or enclosed and do not detract from the desired well-balanced appearance. In fact, the overall appearance is such that one can hardly distinguish the improved T-square from a conventional T-square. Only one edge of the roller is exposed. It may be added, too, that good magnets are cast and cannot be bent or drilled after casting or sintering. Consequently by using small powerful properly chosen and arranged horseshoe-shaped magnets the finished product is highly desirable. In addition it is to be added that not only are the rollers preferably of non-magnetic material such as plastic, the pivot pins are likewise of non-magnetic material.

The operation of this form of the invention appearing in FIGS. 4 to 7 is identical to that previously described.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous m0di fications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

What is claimed as new is as follows:

1. A T-square comprising a conventional head and leg, said leg being disposed at right angles to the length- 7 wise dimension of the head and secured at one end atop portion of said spool projecting beyond cooperating guide maining one at the approximate center line, that is the on the drawing board the rollers provide the desired cooperating relationship wherein at least two or a pair of the rollers will remain in contact with the surface 18. It will edge portions of said plates, and a horseshoe-type magnet located in said recess, cooperable with said spool, and having leg portions thereof embracing the hub portion of the spool between the end heads of said spool.

2. An attachment for the head of a T-square comprising a pair of spaced parallel roller mounting plates, means for fastening the plates together and to lengthwise top and bottom surfaces. of said head, a plurality of spools mounted for free rotation on pins mounted in cooperating lengthwise edge portions of the plates, and a plurality of horseshoe-shaped magnets, one magnet for each spool, each magnet having legs interposed between head portions of the cooperating spool.

3. A T-square comprising a head having a straight guide edge adapted to parallel and travel along an existing straight edge on a draftsmans drawing board, and an elongated complemental leg disposed at right angles to and having one end secured to a median portion of said head, said head having longitudinally spaced notches, one notch being located at each end portion of the head and a third notch aligned with that end of the leg which is secured to the median portion of said head, a top plate in said head in a manner to rollably contact the aforementioned straight edge on said drawing board.

4. An attachment for the underneath planar side of the head of a conventional-type T-square, said attachment comprising a self-contained bodily applicable and removable unit, said unit comprising an elongated housing, said housing embodying an elongated core member provided with several longitudinally spaced notches defining pocketlike recesses, said recesses opening through top and bottom sides and one lengthwise edge of said core-like member, a companion bottom plate parallel to said top plate and underlying and aflixed to the bottom of said core-like member, said plates being secured together and to said core-like member and serving to cover the otherwise open top and bottom sides of said notches and consequently defining individual pocket-like recesses, said top plate being provided on the lengthwise edge with an upstanding attaching and retaining flange, a horseshoe magnet fitted and retained in a centrally positioned one of said recesses, and individual anti-friction rollers mounted for operation in the end recesses, marginal portions of said rollers projecting beyond open marginal portions of the recesses in a manner to'rollably contact a straight edge on a drafting board.

References Cited in the file of this patent FOREIGN PATENTS Great Britain of 1912 Great Britain Feb. 13, 1957 

1. A T-SQUARE COMPRISING A CONVENTIONAL HEAD AND LEG, SAID LEG BEING DISPOSED AT RIGHT ANGLES TO THE LENGTHWISE DIMENSION OF THE HEAD AND SECURED AT ONE END ATOP A MEDIAN PORTION OF SAID HEAD, TOP AND BOTTOM PLATES PARALLEL TO EACH OTHER AND ATTACHED TO AND FACING TOP AND BOTTOM SURFACES OF SAID HEAD, AT LEAST ONE SPOOL PROVIDING A ROLLER, SAID SPOOL BEING LOCATED IN A RECESS BETWEEN SAID PLATES AND BEING CONNECTED TO SAID PLATES FOR FREE ROTATION BY AN ATTACHING AND RETAINING PIVOT PIN, A SEGMENTAL EDGE PORTION OF SAID SPOOL PROJECTING BEYOND COOPERATING GUIDE EDGE PORTIONS OF SAID PLATES, AND A HORSESHOE-TYPE MAGNET LOCATED IN SAID RECESS, COOPERABLE WITH SAID SPOOL, AND HAVING LEG PORTIONS THEREOF EMBRACING THE HUB PORTION OF THE SPOOL BETWEEN THE END HEADS OF SAID SPOOL. 